The present invention relates to a cover strip-off method in an apparatus for cutting and stripping covered wires such as covered electric wires, optical fiber cables, and the like, used in various electric machineries and apparatuses.
Generally, a covered electric wire 31 cut to a predetermined size as shown in FIG. 14 is used in an electronic/electric machine or apparatus. This covered electric wire 31 has a cover 33 on the surface of a core 32 of copper or the like. The cover 33 is made of polyvinyl chloride resin mainly for insulation. The length L1 of the covered electric wire 31, the length L2 of the cover 33, and the exposed lengths of the core 32, that is, the stripped-off lengths L3 and L4 of the cover 33, are configured to predetermined sizes in accordance with the portion where the wire is used.
As an apparatus for automatically configuring such a covered electric wire, the applicant of the present application has proposed an automatic electric wire cutting and stripping apparatus shown in Japanese Patent Unexamined Publication No. Sho-61-273114. The covered electric wire cutting and stripping method in this cutting and stripping apparatus includes steps in which a pair of upper and lower cutting blades facing each other are moved from a standby position where their blade portions do not reach the cover of the covered electric wire to a cutting position where the cutting blades cut the covered electric wire. The cutting blades are moved back to the standby position from the cutting position, and the covered electric wire is moved in its longitudinal direction in the state where the cutting blades have been moved to the standby position. This covered electric wire cutting and stripping method further has a step in which the above-mentioned cutting blades are moved from the standby position to an incision position so as to form an incision in the cover of the covered electric wire, and thereafter, the cutting blades are moved to a non-interference position retracted from the incision position or from a core of the covered electric wire within a range where the blade portions of the cutting blades can catch the cover. The core of the covered electric wire and the cover at the end portion of the covered electric wire are moved relative to each other from the state where the cutting blades have been moved to the non-interference position so as to strip the cover on the core by the cutting blades, and thereafter, the cutting blades are moved back to the standby position from the non-interference position.
In the above-mentioned conventional cover incising and stripping method, the cover is incised by the cutting blades, and the cutting blades are moved within a range where their blade portions can catch the cover. Thereafter, the covered wire is relatively moved in the stripping direction. Accordingly, the blade portions of the cutting blades are prevented from scratching the core at the time of the operation of stripping the cover, and the core is prevented from being injured or broken. In the case where the cover is thin, however, when the cutting blades are moved from the incision position where the cutting blades contact the core, the cutting blades can catch the end surface of the cover such that the cutting blades are detached from the incision end surface of the cover by the cover stripping resistance at the initial time, thereby making it impossible to perform the cover stripping operation. In addition, even in the case where the cover is thick, if the length of the stripping of the cover is so large that the cover stripping resistance is large at the time of starting the cover stripping operation, the cutting blades are retracted by the large cover stripping resistance from the incision position where the cutting blades contact the core so that the cutting blades are detached from the cover, thereby making it impossible for the cutting blades to perform the cover stripping operation.